The present invention relates generally to an electromagnetic induction generator for use in a tubular, such as a tubular deployed in a subterranean well, and, in one or more embodiments, to such an electromagnetic induction generator wherein one or both of at least one conductive coil and at least one Halbach array of magnets is rotated relative to the other to increase the electric current generated through electromagnetic induction.
As downhole tools used to perform wellbore construction operations for oil and gas wells are becoming more sophisticated, these tools require increased electrical power to operate ancillary systems, such as electronics and on-board control mechanisms. An example is rotary steerable systems that are used to drill wells directionally. If a tool is mechanically reliable, the operational lifespan thereof prior to servicing is typically limited by the life of the battery used to power the tool while in the well bore. Therefore, it is desirable to extend the life of such tools in order to utilize their functionality during longer stretches of wellbore construction, and to avoid unnecessary and expensive trips in/out of the well bore to replace or recharge batteries.
Existing downhole electrical power generators that use fluid-driven turbines are not ideal because of the inherent fluid pressure drop associated with using a fluid turbine. As an alternative to fluid driven turbines, batteries, such as lithium batteries, were introduced to power downhole equipment. However, such batteries must be replaced or recharged. Accordingly, such a battery may be removably mounted so that when it is determined that the stored power is running low, the battery can be removed and replaced by with a fully charged battery. Alternatively, the battery may be rechargeable and arranged to be charged in situ. For example, the battery can be recharged using an electrical cable lowered from the surface, when required, and connected to the battery 30. Alternatively, it may be recharged using a wired drill pipe link in the drill string connected to a power source located at the surface or elsewhere. If for any reason the battery cannot be charged in situ, then the tool assembly containing the drained battery will often need to be pulled from its downhole location and replaced at the well head, which can be time-consuming and expensive.
Accordingly, a need exists for assemblies and processes for generating electricity to power downhole equipment, to recharge batteries used in a downhole environment or for both reasons when performing wellbore construction operations, such as drilling operations and certain completion operations, for example a completion operation wherein one or more plugs are drilled out of a well, that does not require tripping equipment in/out of the well, nor energy conveyed from the surface of the earth.